ctest arp pass

libsponge/network_interface.cc

@@ -32,15 +32,121 @@ NetworkInterface::NetworkInterface(const EthernetAddress &ethernet_address, cons
 void NetworkInterface::send_datagram(const InternetDatagram &dgram, const Address &next_hop) {
     // convert IP address of next hop to raw 32-bit representation (used in ARP header)
     const uint32_t next_hop_ip = next_hop.ipv4_numeric();
-
+    auto const &itr_next_hop_eth = _arp_cache.find(next_hop_ip);
-    DUMMY_CODE(dgram, next_hop, next_hop_ip);
+    if (itr_next_hop_eth != _arp_cache.end()) {
+        // found
+        auto const &next_hop_eth = itr_next_hop_eth->second;
+        if (next_hop_eth.first.has_value()) {
+            // a valid arp cache entry
+            EthernetFrame frame;
+            EthernetHeader hdr;
+            hdr.dst = next_hop_eth.first.value();
+            hdr.src = _ethernet_address;
+            hdr.type = EthernetHeader::TYPE_IPv4;
+            frame.header() = hdr;
+            frame.payload() = dgram.serialize();
+            _frames_out.push(frame);
+        } else {
+            // an arp has been sent for it within 5 seconds
+            _suspended_datagrams.push_back(std::make_pair(dgram, next_hop));
+        }
+    } else {
+        // not found and no arp has been sent for the ip
+        _suspended_datagrams.push_back(std::make_pair(dgram, next_hop));
+        ARPMessage arpmsg;
+        arpmsg.opcode = ARPMessage::OPCODE_REQUEST;
+        arpmsg.sender_ethernet_address = _ethernet_address;
+        arpmsg.sender_ip_address = _ip_address.ipv4_numeric();
+        arpmsg.target_ip_address = next_hop_ip;
+        EthernetFrame frame;
+        EthernetHeader hdr;
+        hdr.dst = ETHERNET_BROADCAST;
+        hdr.src = _ethernet_address;
+        hdr.type = EthernetHeader::TYPE_ARP;
+        frame.header() = hdr;
+        frame.payload() = arpmsg.serialize();
+        _frames_out.push(frame);
+        _arp_cache[next_hop_ip] = std::make_pair(std::optional<EthernetAddress>{}, 5 * 1000);
+        // allocate an entry for the ARP Req we sent
+    }
 }
 
 //! \param[in] frame the incoming Ethernet frame
 optional<InternetDatagram> NetworkInterface::recv_frame(const EthernetFrame &frame) {
-    DUMMY_CODE(frame);
+    if (frame.header().dst != _ethernet_address && frame.header().dst != ETHERNET_BROADCAST)
+        return {};
+    if (frame.header().type == EthernetHeader::TYPE_IPv4) {
+        auto payload = frame.payload();
+        InternetDatagram dgram;
+        auto parse_res = dgram.parse(payload);
+        if (parse_res == ParseResult::NoError) {
+            return dgram;
+        }
+    } else if (frame.header().type == EthernetHeader::TYPE_ARP) {
+        if (frame.header().src == _ethernet_address) {
+            cerr << "receive loopback arp req\n";
+            return {};
+        }
+        ARPMessage arpmsg;
+        auto parse_res = arpmsg.parse(frame.payload());
+        if (parse_res != ParseResult::NoError) {
+            return {};
+        }
+        if (arpmsg.opcode != ARPMessage::OPCODE_REPLY && arpmsg.opcode != ARPMessage::OPCODE_REQUEST) {
+            cerr << "unknown ARP opcode\n";
+            return {};
+        }
+        if (arpmsg.opcode == ARPMessage::OPCODE_REQUEST && arpmsg.target_ip_address == _ip_address.ipv4_numeric()) {
+            ARPMessage arpreply;
+            arpreply.opcode = ARPMessage::OPCODE_REPLY;
+            arpreply.sender_ethernet_address = _ethernet_address;
+            arpreply.sender_ip_address = _ip_address.ipv4_numeric();
+            arpreply.target_ip_address = arpmsg.sender_ip_address;
+            arpreply.target_ethernet_address = arpmsg.sender_ethernet_address;
+            // i think this should be directly the requester's EA
+            EthernetFrame framereply;
+            EthernetHeader hdr;
+            hdr.dst = arpmsg.sender_ethernet_address;
+            hdr.src = _ethernet_address;
+            hdr.type = EthernetHeader::TYPE_ARP;
+            framereply.header() = hdr;
+            framereply.payload() = arpreply.serialize();
+            _frames_out.push(framereply);
+        }
+        // no matter what type of arp it is, learn from it
+        _arp_cache[arpmsg.sender_ip_address] =
+            std::make_pair(std::optional<EthernetAddress>{arpmsg.sender_ethernet_address}, 30 * 1000);
+        auto itr_dgram = _suspended_datagrams.begin();
+
+        while (itr_dgram != _suspended_datagrams.end()) {
+            if (_arp_cache.find(itr_dgram->second.ipv4_numeric()) != _arp_cache.end()) {
+                auto dgram = itr_dgram->first;
+                auto next_hop = itr_dgram->second;
+                itr_dgram = _suspended_datagrams.erase(itr_dgram);
+                this->send_datagram(dgram, next_hop);
+            } else {
+                itr_dgram++;
+            }
+        }
+    }
     return {};
 }
 
 //! \param[in] ms_since_last_tick the number of milliseconds since the last call to this method
-void NetworkInterface::tick(const size_t ms_since_last_tick) { DUMMY_CODE(ms_since_last_tick); }
+void NetworkInterface::tick(const size_t ms_since_last_tick) {
+    for (auto &arp_entry : _arp_cache) {
+        if (arp_entry.second.second >= ms_since_last_tick)
+            arp_entry.second.second -= ms_since_last_tick;
+        else
+            arp_entry.second.second = 0;
+    }
+    auto arp_entry = _arp_cache.begin();
+    while (arp_entry != _arp_cache.end()) {
+        if (arp_entry->second.second == 0) {
+            arp_entry = _arp_cache.erase(arp_entry);
+        } else {
+            arp_entry++;
+        }
+    }
+    // TODO: maybe drop packets that couldn't get ARP reply, though not required in this lab
+}

libsponge/network_interface.hh

@@ -7,6 +7,9 @@
 
 #include <optional>
 #include <queue>
+#include <map>
+#include <utility>
+#include <list>
 
 //! \brief A "network interface" that connects IP (the internet layer, or network layer)
 //! with Ethernet (the network access layer, or link layer).
@@ -40,6 +43,13 @@ class NetworkInterface {
     //! outbound queue of Ethernet frames that the NetworkInterface wants sent
     std::queue<EthernetFrame> _frames_out{};
 
+    //! internal map as arp cache, holding mapping from ipv4(numerical form) to MAC addr with expire time.
+    //! if optinal<EthnernetAddress> has no value, it means that a ARP has been sent for the IP within 5 seconds
+    std::map<uint32_t, std::pair<std::optional<EthernetAddress>, size_t> > _arp_cache{};
+
+    //! queue the IP datagrams waiting for ARP reply
+    std::list<std::pair<InternetDatagram, Address> >_suspended_datagrams{};
+
   public:
     //! \brief Construct a network interface with given Ethernet (network-access-layer) and IP (internet-layer) addresses
     NetworkInterface(const EthernetAddress &ethernet_address, const Address &ip_address);